Lindsay Lohan's Asst. Subpoenaed Forced to Testify at Trial

2/23/2013 2:10 PM PST

Lindsay Lohan -- Ex-Assistant Subpoenaed, Forced to Testify at Trial

EXCLUSIVE

Bad news for Lindsay Lohan -- her ex-assistant is being forced to testify in the actress' upcoming "lying to cops" case ... the same assistant who ratted her out to police.

TMZ has learned ... Lindsay's ex-assistant Gavin was served with a subpoena by the L.A. City Attorney's office earlier this month -- meaning he'll have to take the stand in LiLo's trial regarding that June PCH car crash.